1 files changed, 102 insertions, 0 deletions

diff --git a/mm/thrash.c b/mm/thrash.c
new file mode 100644
index 000000000000..11461f7ad830
--- /dev/null
+++ b/mm/thrash.c
@@ -0,0 +1,102 @@
+/*
+ * mm/thrash.c
+ *
+ * Copyright (C) 2004, Red Hat, Inc.
+ * Copyright (C) 2004, Rik van Riel <riel@redhat.com>
+ * Released under the GPL, see the file COPYING for details.
+ *
+ * Simple token based thrashing protection, using the algorithm
+ * described in:  http://www.cs.wm.edu/~sjiang/token.pdf
+ */
+#include <linux/jiffies.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/swap.h>
+
+static DEFINE_SPINLOCK(swap_token_lock);
+static unsigned long swap_token_timeout;
+static unsigned long swap_token_check;
+struct mm_struct * swap_token_mm = &init_mm;
+
+#define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2)
+#define SWAP_TOKEN_TIMEOUT      0
+/*
+ * Currently disabled; Needs further code to work at HZ * 300.
+ */
+unsigned long swap_token_default_timeout = SWAP_TOKEN_TIMEOUT;
+
+/*
+ * Take the token away if the process had no page faults
+ * in the last interval, or if it has held the token for
+ * too long.
+ */
+#define SWAP_TOKEN_ENOUGH_RSS 1
+#define SWAP_TOKEN_TIMED_OUT 2
+static int should_release_swap_token(struct mm_struct *mm)
+{
+        int ret = 0;
+        if (!mm->recent_pagein)
+                ret = SWAP_TOKEN_ENOUGH_RSS;
+        else if (time_after(jiffies, swap_token_timeout))
+                ret = SWAP_TOKEN_TIMED_OUT;
+        mm->recent_pagein = 0;
+        return ret;
+}
+
+/*
+ * Try to grab the swapout protection token.  We only try to
+ * grab it once every TOKEN_CHECK_INTERVAL, both to prevent
+ * SMP lock contention and to check that the process that held
+ * the token before is no longer thrashing.
+ */
+void grab_swap_token(void)
+{
+        struct mm_struct *mm;
+        int reason;
+
+        /* We have the token. Let others know we still need it. */
+        if (has_swap_token(current->mm)) {
+                current->mm->recent_pagein = 1;
+                return;
+        }
+
+        if (time_after(jiffies, swap_token_check)) {
+
+                /* Can't get swapout protection if we exceed our RSS limit. */
+                // if (current->mm->rss > current->mm->rlimit_rss)
+                //      return;
+
+                /* ... or if we recently held the token. */
+                if (time_before(jiffies, current->mm->swap_token_time))
+                        return;
+
+                if (!spin_trylock(&swap_token_lock))
+                        return;
+
+                swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
+
+                mm = swap_token_mm;
+                if ((reason = should_release_swap_token(mm))) {
+                        unsigned long eligible = jiffies;
+                        if (reason == SWAP_TOKEN_TIMED_OUT) {
+                                eligible += swap_token_default_timeout;
+                        }
+                        mm->swap_token_time = eligible;
+                        swap_token_timeout = jiffies + swap_token_default_timeout;
+                        swap_token_mm = current->mm;
+                }
+                spin_unlock(&swap_token_lock);
+        }
+        return;
+}
+
+/* Called on process exit. */
+void __put_swap_token(struct mm_struct *mm)
+{
+        spin_lock(&swap_token_lock);
+        if (likely(mm == swap_token_mm)) {
+                swap_token_mm = &init_mm;
+                swap_token_check = jiffies;
+        }
+        spin_unlock(&swap_token_lock);
+}